Amine gas treating, also known as gas sweetening and acid gas removal, refers to a group of processes that use aqueous solutions of various alkanolamines (commonly referred to simply as amines) to remove hydrogen sulfide (H₂S) and carbon dioxide (CO₂) from gases. It is a common unit process used in refineries, petrochemical plants, natural gas processing plants and other industries.

Processes within oil refineries or natural gas processing plants that remove hydrogen sulfide and/or mercaptans are commonly referred to as sweetening processes because they result in products which no longer have the sour, foul odors of mercaptans and hydrogen sulfide.

There are many different amines used in gas treating:

• Monoethanolamine (MEA)
• Diethanolamine (DEA)
• Methyldiethanolamine (MDEA)
• Diisopropylamine (DIPA)
• Aminoethoxyethanol (diglycolamine) (DGA)

The most commonly used amines in industrial plants are the alkanolamines MEA, DEA, and MDEA.

Amines are also used in many oil refineries to remove sour gases from liquid hydrocarbons such as liquified petroleum gas (LPG).

[edit] Description of a typical amine treater

Gases containing H₂S or both H₂S and CO₂ are commonly referred to as sour gases or acid gases in the hydrocarbon processing industries.

A typical amine gas treating process (as shown in the flow diagram below) includes an absorber unit and a regenerator unit as well as accessory equipment. In the absorber, the downflowing amine solution absorbs H₂S and CO₂ from the upflowing sour gas to produce a sweetened gas stream (i.e., an H₂S-free gas) as a product and an amine solution rich in the absorbed acid gases. The resultant "rich" amine is then routed into the regenerator (a stripper with a reboiler) to produce regenerated or "lean" amine that is recycled for reuse in the absorber. The stripped overhead gas from the regenerator is concentrated H₂S and CO₂. In oil refineries, that stripped gas is mostly H₂S, much of which often comes from a sulfur-removing process called hydrodesulfurization. This H₂S-rich stripped gas stream is then usually routed into a Claus process to convert it into elemental sulfur. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from refineries and other hydrocarbon processing plants. ^[1][2] Another sulphur-removing process is the WSA Process which recovers sulphur in any form as concentrated sulphuric acid. In some plants, more than one amine absorber unit may share a common regenerator unit.

Process flow diagram of a typical amine treating process used in industrial plants

In the steam reforming process of hydrocarbons to produce gaseous hydrogen for subsequent use in the industrial synthesis of ammonia, amine treating is one of the commonly used processes for removing excess carbon dioxide in the final purification of the gaseous hydrogen.

[edit] New amine-based solvents and materials for gas processing

As profiled in the July 13, 2009 issue of C&E News, ION Engineering is commercializing technology using ionic liquids and amines for CO₂ capture and natural gas sweetening.

Other examples of new amine-based materials can be found in papers by Davis' group at the University of South Alabama.^[3][4]

[edit] See also

• Ammonia production
• Hydrodesulfurization
• WSA Process
• Claus process
• Selexol
• Rectisol
• Amine
• Ionic liquids

[edit] References

[edit] External links

• Selecting Amines for Sweetening Units, Polasek, J. (Bryan Research & Engineering) and Bullin, J.A. (Texas A&M University), Gas Processors Association Regional Meeting, Sept. 1994.

• Natural Gas Supply Association Scroll down to Sulfur and Carbon Dioxide Removal

• Sweetening LPG's with Amines, Holmes, J.W. (Bryan Research & Engineering), Spears, M.L. (Bryan Research & Engineering), and Bullin, J.A. (Texas A&M University), Chemical Engineering Progress, May 1984

• Description of the classic book on gas treating by Arthur Kohl & Richard Nielsen. Gas Purification (Fifth Edition ed.). Gulf Publishing. ISBN 0-88415-2200.